This invention relates to a bending device and a flexible tube structure which are used, for example, in an endoscope.
As is well known, an endoscope comprises a hollow body, a flexible insertion portion extending from a front end of the body, a flexible bending portion extending from a distal end of the insertion portion, and a rigid portion formed on a distal end of the bending portion.
In conventional bending portions (bending devices) for an endoscope as disclosed in Japanese Utility Model Publication No. 31669/73 and Japanese Laid-Open (Kokai) Utility Model Application No. 130602/82, a number of tubular elements are arranged axially. Each tubular element has axially-extending connective portions, and the connective portions of the adjacent tubular elements are connected together by riveting, thereby interconnecting the adjacent tubular elements in a manner to allow a relative angular movement therebetween. A guide portion is formed on the inner peripheral surface of each tubular element, or a guide member is fixedly secured to the inner peripheral surface of each tubular element. An operating wire is guided by such guide means. The proximal end of the operating wire is connected to an manipulating member mounted on the above body whereas the distal end is fixedly secured to the rigid portion. The manipulating member is operated to pull the operating wire, so that the bending portion is bent or curved so as to direct the rigid portion in a desired direction. The bending portion has an axially-extending internal space, and a bundle of optical fibers for transmitting illumination light, a bundle of optical fibers for transmitting an image, and a guide tube for guiding a forceps are passed through this internal space.
In the bending portion of the above construction, much time and labor are required for the working or processing of the tubular elements and for pressing rivets. This results in an increased manufacturing cost of the bending portion. Particularly when manufacturing the bending portion of a narrow construction, the manufacturing cost has been very high. Further, since the guide portion or the guide member for guiding the operating wire is projected from the inner peripheral surface of the tubular element, there is a possibility that the optical fiber bundles, etc., inserted in the internal space may be damaged by the guide portion or the guide member when the bending portion is bent.
A conventional insertion portion (flexible tube structure) for an endoscope, as disclosed in Japanese Laid-Open Patent Application No. 36/84, comprises a holder coil formed by winding a strip-like plate, a braid tube formed around the outer periphery of the holder coil, and an outer sheath of a resin covering the braid tube. Any two adjacent turns of the holder coil are spaced apart from each other.
The insertion portion of the above construction is excellent in flexibility, but has a drawback that it contracts axially. This drawback arises from the facts that the braid tube hardly offers a resistance to a compressive force tending to axially contract the insertion portion, and that the holder coil and the outer sheath are resilient in the axial direction. Therefore, particularly when the insertion portion is of the narrow type so as to be inserted into the trachea or the blood vessel, the insertion portion is axially contracted due to resistances offered by the trachea or the blood vessel, and can not be smoothly inserted thereinto.
With respect to another prior art flexible tube structure, Japanese Laid-Open Utility Model Application No. 18102/87 discloses a guide tube for guiding a forceps in an endoscope. This guide tube comprises one coil, and a resilient resin tube.